1. Field of the Invention
The invention relates to an optical storing apparatus for recording and reproducing information by using a laser beam and a recording and reproducing method of an optical storage medium. More particularly, the invention relates to an optical storing apparatus for optimizing a retry in the case where a read error occurs in the recording and reproducing operation of an optical storage medium including an MSR medium to record and reproduce data at a density smaller than a beam diameter and a recording and reproducing method of an optical storage medium.
2. Description of the Related Arts
In recent years, an optical disk is highlighted as an external storage medium of a computer. In the optical disk, by forming magnetic recording pits on the submicron order onto the medium by using a laser beam, a recording capacity can be remarkably increased as compared with that of a floppy disk or a hard disk so far as an external storage medium. Further, in a magnetooptic disk as a perpendicular magnetic storage medium using a rare earthxe2x80x94transition metal system material, information can be rewritten and the future development is more and more expected.
The optical disk has a memory capacity of, for example, 128 MB, 230 MB, 540 MB, or 640 MB for one side of the disk of 3.5 inches. The 128 MB medium and 230 MB medium are based on a pit position modulation (PPM) recording. The 540 MB medium and 640 MB medium are based on a pulse width modulation (PWM) recording. This means that one optical disk has a memory capacity of 128 to 640 floppy disks when considering a fact that a memory capacity of one floppy disk of 3.5 inches is equal to about 1 MB. As mentioned above, the optical disk is a rewritable storage medium of a very high recording density. However, for preparations for a future multimedia era, it is necessary to further raise the recording density of the optical disk to a value larger than the present one. To raise the recording density, further more pits have to be recorded on the medium. For this purpose, it is necessary to further reduce the size of pit and to narrow an interval between the pits. In case of raising the recording density by such a method, although it is necessary to further reduce a wavelength of a laser beam to a value shorter than the present wavelength of 670 nm, when considering the case of putting into practical use, the pit size has to be reduced at the existing wavelength of 670 nm. In this case, as for the recording, by controlling a power of the laser beam, the pit smaller than the beam diameter can be formed. As for the reproduction, however, if the pit smaller than the beam diameter is reproduced, a crosstalk with the adjacent pit increases. In the worst case, since information of the adjacent pit is also included in a reproducing beam, such a method is very difficult when considering practicality.
As a method of reproducing a pit smaller than the beam diameter by using the beam of the existing wavelength of 670 nm, there is a magnetooptic recording and reproducing method represented by JP-A-3-93058 and is known as a recording and reproducing method by an MSR (Magnetically induced Super Resolution). The above method has two methods of an FAD (Front Aperture Detection) system and an RAD (Rear Aperture Detection) system. According to the FAD system, as shown in FIGS. 1A and 1B, an MSR medium is divided into a recording layer 320 and a reproducing layer 316 on a substrate 311 and a reproducing magnetic field Hr is applied in a state where a laser spot 322 of a read beam is irradiated, thereby reproducing. In this instance, in the portion where the reproducing layer 316 is the recording pit, a magnetic coupling of a switching layer 318 which is formed at a boundary with the recording layer 320 is released in dependence on a temperature distribution of the medium heating by the laser spot 322 and such a portion is influenced by the reproducing magnetic field Hr and becomes a mask. On the other hand, with regard to the portion of the next recording pit, the magnetic coupling of the switching layer 318 is held and such a portion becomes an aperture 324. Therefore, like a laser spot 322, only a pit 330 of the aperture 324 can be read without being influenced by an adjacent pit 328.
According to the double mask RAD system, as shown in FIGS. 2A and 2B, the MSR medium is constructed by three layers of the reproducing layer 316, an intermediate layer 317, and the recording layer 320 on the substrate 311. A reproducing laser power upon reproduction is slightly raised and information is read. Upon reading, depending on a temperature distribution of the medium heating by a laser spot 334 of the read beam, a front mask 336, an aperture 338 in which magnetization information of the recording layer 320 is transferred to the reproducing layer 316, and a rear mask 337 are formed in the reproducing layer 316. That is, in the front mask 336 at a low temperature by the read beam laser spot 334, no signal is derived because the reproducing layer 316 has been initialized by a reproducing magnetic field 332. In the aperture 338 at an intermediate temperature, since the intermediate layer 317 is perpendicularly magnetized, its coupling force is enhanced, the magnetization information of the recording layer 320 is transferred to the reproducing layer 316, and a signal is derived. In the rear mask 337 at a high temperature, since it is close to the Curie temperature of the intermediate layer 317, the coupling force between the recording layer 320 and reproducing layer 316 decreases and the magnetization of the reproducing layer 316 is aligned in the direction of the reproducing magnetic field 332. The magnetization information of the recording layer 320 transferred to the reproducing layer 316 is converted into an optical signal by a magnetooptic effect (Kerr effect or Faraday effect), so that data is reproduced. In this instance, as compared with a pit 328 of the recording layer 320 which is being read out at present, in the pit 330 of the recording layer 320 to be subsequently read out, since the information is not transferred because of the formation of the front mask 336 by initial magnetization information of the reproducing layer 316, even if the recording pit is smaller than the laser spot 334, no crosstalk is generated and the pit smaller than the beam diameter can be reproduced. Further, if the double mask RAD is used, since the area of the recording layer 320 other than the reproducing portion is in a state where it has been masked by the initialized reproducing layer 316, a pit interference from the adjacent pit does not occur and the pit interval can be further narrowed. The crosstalk from the adjacent track can be also suppressed. Thus, a track pitch can be narrowed more than that of the FAD and the reproduction can be performed at a high density even by using the beam of the existing wavelength of 680 nm.
However, in the conventional optical disk apparatus using the MSR medium as mentioned above, there is a problem such that unless the reproducing magnetic field which is used upon reproduction and the reading power are strictly controlled, the proper reproducing operation cannot be performed. This is because, for example, when a reproducing power Pr of the laser beam in the FAD system of FIGS. 1A and 1B is too small, a forming range of the mask 326 in FIG. 1B by the magnetization of the reproducing layer 316 decreases, the pit 328 is not masked, and a crosstalk occurs. When the reproducing power Pr is too strong, the forming range of the mask 326 is widened, the pit 330 is also partially masked, a reproducing level decreases, and an error occurs. At the same time, the reproducing magnetic field Hr also acts on the recording layer 320 and there is a possibility that the recording data is erased. When the reproducing power and the reproducing magnetic field are too small in the double mask RAD system of FIGS. 2A and 2B, the coupling range by the beam heating of the reproducing layer 316 is not widened, no aperture is formed, and the pit 328 in FIG. 2B is not reproduced. When the reproducing power and the reproducing magnetic field are too strong, an erasing range by the beam heating of the initialization magnetic field of the reproducing layer 316 is narrowed, a forming range of the front mask 336 is widened, and the pit 328 is also partially masked. The aperture 338 decreases, the reproducing level decreases, and an error occurs. At the same time, if the reproducing power is too strong, it also acts on the recording layer 320 and there is a possibility that the recording data is erased. To solve such a phenomenon, the method of merely adjusting the reproducing magnetic field or the reproducing power is insufficient and such a phenomenon also depends on an environmental temperature in the apparatus which decides a temperature of the storage medium. That is, when the environmental temperature in the apparatus changes to the low temperature side, a laser power to heat the reproducing layer to an aperture forming temperature is needed. On the contrary, when the environmental temperature changes to the high temperature side, since it is sufficient to slightly heat the reproducing layer to a rear mask forming temperature, it is necessary to reduce the reproducing power. When the reading of a certain sector of the MSR medium based on a read access fails, a read retry to read again by using values of the reproducing power and reproducing magnetic field adjusted to optimum values is performed. However, if the environmental temperature or the like in the apparatus is out of conditions upon adjustment of the reproducing magnetic field to the optimum value, even if the retry is performed many times, the reading operation does not succeed and a retry out finally occurs. The sector is determined to be a defective sector, and an alternating process is executed. Therefore, when the read error occurs, it takes time until the retry succeeds. Further, if use conditions of the apparatus are largely changed, the read error often occurs due to the unsuccessful retry and there is a problem of deterioration of processing performance. A similar problem of the read retry also occurs in a verify retry when an error occurs due to a verification because the erasure, writing, and verification are performed in the writing operation. The problem of the unsuccessful retry in the read retry and verify retry similarly occurs in not only the MSR medium which needs the reproducing magnetic field but also an ordinary MO medium.
According to the invention, an optical storing apparatus for reducing the occurrence of a read error of an MSR medium by devising a retrying process and a recording and reproducing method of an optical storage medium are provided.
First, the invention uses an MSR medium (optical storage medium) in which at least a recording layer to record data and a reproducing layer to reproduce the data recorded on the recording layer are formed on a substrate. A recording unit records data to the recording layer of the MSR medium at a recording density smaller than a beam diameter of a laser beam. A reproducing unit combines a reproducing magnetic field and a reproducing laser power which are necessary for reproduction and sets them to optimum values, thereby reproducing the data recorded on the recording layer of the MSR medium at the recording density smaller than the beam diameter. In addition, the invention is characterized in that a read retrying processing unit is provided and, at the time of a read retry when a read error occurs, a value of the reproducing magnetic field is changed and the reproducing operation is retried. As mentioned above, according to the invention, the value of the reproducing magnetic field is changed at the time of the read retry of the MSR medium and the read retry is performed by the changed reproducing magnetic field, thereby making the retry succeed and reducing a frequency of the occurrence of the read error due to the retry out.
The read retry processing unit changes the reproducing magnetic field at the time of the read retry in accordance with at least any one of each zone formatted in the MSR medium, each area obtained by dividing a recording area of the MSR medium into a plurality of areas, and a temperature in the apparatus. Since an intensity of the reproducing power or reproducing magnetic field that is optimum for reproduction of the MSR medium differs depending on each zone and each area of the medium and, further, the temperature in the apparatus at that time, by changing the reproducing power or reproducing magnetic field to the proper value in accordance with those conditions, the occurrence frequency of the read error is reduced. The read retry processing unit determines a test offset xcex94Pr1 or xcex94H1 of the optimum reproducing power or optimum reproducing magnetic field by a test read and changes it to the reproducing power (Pr+xcex94Pr1+xcex94Pr2) or reproducing magnetic field (H+xcex94H1+xcex94H2) obtained by adding the test offset xcex94Pr1 or xcex94H1 and a predetermined retry offset xcex94Pr2 or xcex94H2 to a predetermined default value Pr and H, respectively. As mentioned above, at the time of the read retry, after the optimum reproducing power or optimum reproducing magnetic field adapted to the use conditions at that time was determined by the test read, the optimum reproducing power or optimum reproducing magnetic field is changed to the value for retry and the data is read out again. Thus, the reproducing power or reproducing magnetic field can be changed to the optimum reproducing power or optimum reproducing magnetic field adapted to the change in actual use conditions. As the learning advances, the reading operation can be made successful by the retries of the small number of times.
According to the invention, there is provided a recording and reproducing method of an MSR medium, comprising:
a recording step of recording data to a recording layer of an MSR medium at a recording density smaller than a beam diameter of a laser beam by using the MSR medium (optical storage medium) in which at least a recording layer to record data and a reproducing layer to reproduce the data recorded on the recording layer are formed on a substrate;
a reproducing step of reproducing the data recorded on the recording layer of the MSR medium at the recording density smaller than the beam diameter by combining a reproducing magnetic field and a reproducing laser power which are necessary for reproduction and setting them to optimum values; and
a read retry step of changing the value of the reproducing magnetic field and retrying the reproducing operation at the time of a read retry when a read error occurs in the reproducing step.
The details of the recording and reproducing method of the MSR medium are also substantially the same as those of the apparatus construction.
According to the invention, there are provided optical storing apparatus and method in which in a read retry or a verify retry which is executed while changing the setting of parameters, parameter set information when the retry is successful is stored as statistic information, the updating of the optimum parameters by a learning process of the statistic information is performed, and conditions of the retry success are reflected, thereby reducing the occurrence of the read error.
The optical storing apparatus of the invention comprises: a recording unit for recording data onto the optical storage medium by a laser beam; and a reproducing unit for reproducing the data recorded on the optical storage medium by setting parameters necessary for reproduction to optimum values. As for the optical storing apparatus, the invention is characterized in that a read retry processing unit (retry processing unit) is further provided, the read retry is repeated while changing the setting of the parameter set values at the time of the read retry when a read error occurs in the reproducing unit, the parameter set values are stored as statistic information when the retry succeeds, and the parameter set values are updated by the learning process based on the statistic information. The parameter set values are usually values in which the test offsets obtained when the optimum parameters are determined by the testing process were added to the defaults. As mentioned above, according to the optical storing apparatus of the invention, when the read retry succeeds, the parameter set values at the time of success are stored as statistic information, the optimum parameters are automatically updated by the learning process of the statistic information, the conditions of the retry success are reflected to the optimum parameters, and the number of times of read retry until the success thereof is reduced, thereby raising a success ratio, reducing a frequency of occurrence of the read error due to a failure of the retry (retry out), and improving the stability of the reading operation.
Further, at the time of the verify retry when the read error occurs in the recording unit due to the verification, the read retry processing unit similarly repeats the verify retry while changing the setting of the parameter set values, stores the parameter set values as statistic information at the time of the retry success, and updates the parameter set values by the learning process based on the statistic information. Thus, the number of times of verify retry until the success thereof when the read error occurs due to the verification subsequent to the erasure and writing in the writing operation is reduced and the frequency of occurrence of the read error due to the retry failure is decreased, thereby improving the stability of the writing operation. In the case where the MSR medium (Magnetically induced Super Resolution medium) in which data is recorded at a recording density smaller than the beam diameter of the laser beam is used as an optical storage medium, in the optical storing apparatus of the invention, a reproducing magnetic field H, a reading power Pr, a cut-off frequency Fc and a boost Fb of a low pass filter, a slice level S of a slicing circuit, a window value (window delay time) W of a data discriminator, and a focusing offset FCO are set as parameters for reproduction, and at the time of the read retry, the read retry is repeated while sequentially switching a plurality of kinds of parameters and changing the setting thereof. In case of using a magnetooptic medium such as an MO medium in which data is recorded at a recording density depending on the beam system of the laser beam as an optical storage medium, according to the optical storing apparatus of the invention, the reading power Pr, cut-off frequency Fc and boost Fb of the low pass filter, slice level S of the slicing circuit, window value (window delay time) W of the data discriminator, and focusing offset FCO excluding the reproducing magnetic field H peculiar to the MRS medium are set as parameters for reproduction. At the time of the read retry, the read retry is repeated while sequentially switching a plurality of kinds of parameters and changing the setting thereof. At the time of the read retry, the read retry processing unit performs the read retry while alternately (like a toggle) repeating the change of the setting of the parameters to add the retry offsets to the parameter set values and the change of the setting of the parameters to subtract the retry offsets from the parameter set values, and stores the parameter set values at the time of success and information indicating whether the retry offsets have been added or subtracted as statistic information. For example, at the first time of the retry, the retry offsets are added to the parameter set values (=default+test offsets) at that time. In the second retry in which the retry fails, the retry offsets are subtracted from the parameter set values (=default+test offsets). Thus, the setting of the parameters is changed in a range in which a change amount on the plus side and that on the minus side around the parameter set values as centers are almost equal, an opportunity of retry success is enhanced, and the retry is made successful by the retries of the small number of times, thereby raising a success ratio. Since the setting of the parameters is changed almost equally in the plus and minus directions around the default as a center, a situation such that the number of times of retry due to the change in parameters increases and the parameters are rapidly away from the default and reach limit values can be avoided. Upon updating of the parameter set values based on the statistic information, when an absolute value of the sum of the number of times of addition of the retry offsets which succeeded and the number of times of subtraction of the retry offsets which succeeded is equal to or larger than a predetermined threshold value on the basis of the statistic information, the test offsets which are added to the default are updated so that the parameters are close to the parameter set values which made the retry successful. For example, the test offsets which are added to the default are increased or decreased by only the half of the retry offsets which made the retry successful, thereby updating the optimum parameters. As mentioned above, the statistic information of the parameter set values which made the retry successful is learned and the parameters which are used in the ordinary reading or verification are updated in accordance with a statistic tendency of the parameters which make the retry successful, so that errors in the subsequent reading or verification can be reduced.
The retry processing unit changes the parameter set values in accordance with at least any one of each zone which has been formatted onto the optical storage medium, each area obtained by dividing a recording area of the optical storage medium into a plurality of areas, and a temperature in the apparatus. Therefore, the retry processing unit prepares the parameter set values (default+test offsets) and the retry offsets which are used to change the setting of the parameters in accordance with each zone formatted onto the optical storage medium, each area obtained by dividing a recording area of the optical storage medium into a plurality of areas, and the temperature in the apparatus and changes the setting of the parameters by adding the retry offsets to the corresponding parameter set values on the basis of the zone and area and the temperature in the apparatus at the time of retry. Thus, the setting change of the parameters at the time of retry can be optimized in accordance with the zone and area of the optical storage medium and the temperature in the apparatus and the retry success ratio can be improved.
The optical storing apparatus of the invention further has a test processing unit for deciding test offsets which are added to the default that gives the optimum parameter set values by a test read and performing the next test read when the elapsed time from the test reading timing reaches a predetermined time or when a temperature change exceeding a predetermined value in which the apparatus temperature at the time of test read is set to a reference temperature occurs. In this case, when the parameters are updated on the basis of the statistic information in which the parameter set information of the retry success has been stored, the read retry processing unit initializes the elapsed time of the test processing unit, updates the reference temperature to the temperature in the apparatus at the time of the retry success, and allows the next test read to be discriminated. Thus, the process to update the parameters which are used in the ordinary reading or verification on the basis of the parameter set values obtained by the success of the read retry or the write retry is regarded as a process similar to the testing process to decide the optimum parameters in the test processing unit. Since the retry is assembled into a part of the testing process, a frequency of occurrence of the testing process which is executed by interrupting the access to the medium is reduced and the whole access performance is improved.
In the optical storing apparatus of the invention, in the read retry processing unit, when the verify retry is finished unsuccessfully, the writing operation of the erasure, writing, and verification is repeated by the write retry processing unit while changing the setting of the writing power to record data onto the optical storage medium. As mentioned above, even if the read retry is finished unsuccessfully, by further repeating the write retry while changing the writing power, a success ratio of the retry can be further improved. In this instance, at the time of the write retry, the retry processing unit repeats the write retry while alternately performing the change of the setting of the parameters to add the retry offsets to the set value of the writing power and the change of the setting of the parameters to subtract the retry offset from the writing power set value. When the write retry is finished successfully, the retry processing unit stores the successful writing power set value and information indicating whether the retry offsets have been added or subtracted as a learning result. When an absolute value of the sum of the number of times of addition of the successful retry offsets in the learning result and the number of times of subtraction of the successful retry offsets is equal to or larger than a predetermined threshold value, the retry processing unit updates the writing power set value so as to approach the latest writing power set value by which the retry succeeded. Upon write retry, the retry processing unit changes the writing power in accordance with at least any one of each zone formatted onto the optical storage medium, each area obtained by dividing the recording area of the optical storage medium into a plurality of areas, and the temperature in the apparatus.
According to the invention, there is provided an optical storing apparatus in which information of the successful read retry is stored as statistic information and, at the time of the next read retry, conditions of the read retry of a high success ratio are extracted from the statistic information, thereby improving a retry success ratio.
The optical storing apparatus of the invention comprises: a recording unit for recording data onto an optical storage medium by a laser beam; and a reproducing unit for reproducing the data recorded on the optical storage medium by setting parameters which are necessary for reproduction to optimum values. The invention is characterized in that a retry processing unit is further provided and at the time of the read retry when a read error occurs in the reproducing unit, the retry processing unit performs a read retry of a high success ratio on the basis of past successful retry information and stores the successful retry information at the time of the retry success. Since the successful retry information is reflected to the next read retry as mentioned above, a success ratio of the retry which is executed while changing the setting by switching a plurality of kinds of parameters is remarkably raised, and the number of times of retry until it succeeds decreases and a retry execution time is reduced as compared with those of the retry which is performed while sequentially switching a plurality of kinds of parameters and changing the setting thereof in accordance with a fixed predetermined order.
At the time of a verify retry when a read error occurs in the recording unit due to the verification, the retry processing unit further performs the read retry on the basis of past successful retry information and stores the successful retry information at the time of the retry success. With respect to the retry for the read error in the verification subsequent to the erasure and writing of the writing operation as mentioned above as well, the number of times of retry until the retry success is similarly decreased and the retry execution time is reduced. The retry processing unit executes the retry while switching a plurality of kinds of parameters and changing the setting thereof, and the successful parameter set values are stored as statistic information. At the time of the new read retry, the retry processing unit starts the read retry from the previous successful parameter set values, and the successful parameter set values when the retry succeeds are stored. Thus, the previous successful specific parameter set values are used in the next retry and, unless the retry conditions are changed like a reading of the continuous sectors, the retry can be succeeded by one retry. The retry processing unit executes the retry while switching a plurality of kinds of parameters and changing the setting thereof, and the successful parameter set values and the number of times of success for every parameter are stored as statistic information. At the time of the new read retry, the parameter set values are sequentially selected in accordance with the order from the large number of times of success in the statistic information, and the read retry is repeated. As mentioned above, since the number of times of past success has been stored as statistic information with respect to each parameter, at the time of the new retry, the specific parameter set values of the highest success ratio are selected and the retry is executed. The number of times of retry until the success is reduced and the retry execution time is decreased.
In the optical storing apparatus of the invention, when the MSR medium (Magnetically induced Super Resolution medium) in which data is recorded at a recording density smaller than that of the beam system of the laser beam is used as an optical storage medium, the retry is executed while switching a reproducing magnetic field, a reading power, a cut-off frequency and a boost of a low pass filter, a slice level of a slicing circuit, a window value (window delay time) of a data discriminator, and a focusing offset as parameters and changing the setting thereof. When a magnetooptic medium such as an MO medium or the like in which data is recorded at a recording density depending on the beam system of the laser beam is used as an optical storage medium, the retry is executed while switching the reading power, the cut-off frequency and boost of the low pass filter, the slice level of the slicing circuit, the window value (window delay time) of the data discriminator, and the focusing offset as parameters excluding the reproducing magnetic field that is peculiar to the MSR medium and changing the setting thereof. At the time of the read retry, the retry processing unit alternately repeats the setting change of the parameters to add the retry offsets to the parameter set values and the setting change of the parameters to subtract the retry offsets from the parameter set values. The retry processing unit stores the statistic information of the parameter setting in the successful retry in accordance with any one of the temperature in the apparatus, each zone formatted onto the medium, the kind of optical storage medium, and the seek distance. As for various parameters which are used to retry, since the retry success ratio differs depending on the condition of the temperature in the apparatus, the medium zone, the kind of optical storage medium, or the seek distance, by selectively using the parameters in accordance with each condition, the retry success ratio can be further improved. As for the temperature in the apparatus, for example, there is a case where although the retry succeeds at 40xc2x0 C. by the retry in which the set reading power is changed, when the temperature rises to 50xc2x0 C., the retry succeeds by the retry in which the set focusing offset is changed. Therefore, the successful parameter set values and the number of times of success are separately stored every apparatus temperature and, at the time of retry, the retry of the parameters of a high success ratio is selected from the statistic information corresponding to the apparatus temperature and is executed. With respect to the medium zone, since a recording frequency differs every zone, a possibility that the retry which succeeds in the innermost rim is proper in the outermost rim is small. Therefore, the statistic information of the successful retry is stored every zone, and at the time of retry, the parameter information of a high success ratio is selected from the statistic information corresponding to the present zone and the retry is executed. As for the medium kind, for example, there are a 128 MB medium, a 230 MB medium, a 540 MB medium, and a 640 MB medium as MO media. The 128 MB medium and 230 MB medium are based on the PPM recording. The 540 MB medium and 640 MB medium are based on the PWM recording. Further, there is an MSB medium of 1.3 GB. As mentioned above, since the recording and reproducing method differs when the medium kind differs, the statistic information of the successful retry is stored every medium, the parameter information of a high success ratio is selected from the statistic information corresponding to the medium kind at the time of retry, and the retry is executed. Further, as for the read error occurring due to the sector positioning accompanied with the seeking operation, since the parameters of the successful retry differ depending on the seek distance, the statistic information of the successful retry is stored every seek distance. At the time of the retry of the new seek positioning, the parameter information of a high success ratio is selected from the statistic information corresponding to the seek distance at that time and the retry is executed.